CN108816258A - A kind of hollow carbon material, preparation method and its application in catalytic electrolysis aquatic products hydrogen in situ for adulterating hollow phosphatization cobalt nanoparticle - Google Patents

Abstract

The invention discloses a preparation method of a dodecahedral hollow carbon material doped with hollow cobalt phosphide nanoparticles in situ and its application in catalytic electrolysis of water for hydrogen production, belonging to the technical field of catalytic electrolysis of water for hydrogen production. The specific steps are: (1) preparation of metal organic framework material ZIF‑67 with dodecahedral morphology containing cobalt ions; (2) reaction of metal organic framework material ZIF‑67 containing cobalt with dopamine monomer to form (3) preparation of cobalt oxide/carbon composite hollow nanomaterials; (4) preparation of hollow cobalt phosphide/carbon composite hollow nanomaterials. The size of the material can be adjusted according to the size of ZIF-67; in the performance test of catalytic electrolysis of water to produce hydrogen, the electrode material used as the cathode showed very good electrocatalytic activity and stability. Therefore, the material of the present invention has a very good application prospect as an electrode material for catalytic electrolysis of water to produce hydrogen.

Description

Hollow carbon material and preparation method of in-situ doped hollow cobalt phosphide nanoparticles and its application in catalytic electrolysis of water for hydrogen production

technical field

The invention belongs to the technical field of hydrogen production by catalytic electrolysis of water, and specifically relates to a hollow carbon material with dodecahedral morphology doped with hollow cobalt phosphide nanoparticles in situ, a preparation method and its application in hydrogen production by catalytic electrolysis of water.

Background technique

Due to the global energy crisis and related environmental problems, researchers are trying to find renewable energy that can replace fossil fuels, and electrolysis of water to produce hydrogen is a very promising way. Due to the advantages of high energy conversion efficiency, almost no pollution, and broad application prospects, hydrogen production by electrolysis of water has attracted extensive attention of researchers on electrode materials. At present, platinum group metals have the highest hydrogen production activity, but the disadvantages of high cost and low output limit their wide application. Therefore, the exploration of non-noble metal materials with high catalytic activity has received more attention. Although many emerging materials have some obvious advantages compared with noble metal materials, current electrode materials for hydrogen production still have some disadvantages, such as complex fabrication process, low catalytic activity, and small specific surface area. There are two main factors affecting catalytic activity, one is the interaction energy between metal and hydrogen, and the other is the structure and specific surface area of the material. In this regard, the above problems can be effectively overcome by using a hollow carbon material with a large specific surface area and loading transition metal nanoparticles with high hydrogen adsorption capacity in it. For example, Chen's research group used the metal organic framework material ZIF-8@ZIF-67 with a core-shell structure as a template ^[1] , and after carbonization and phosphating, a composite material with a hollow structure and containing cobalt phosphide nanoparticles was prepared. The material exhibits excellent catalytic performance for hydrogen and oxygen production in water electrolysis (the overpotentials are 115mV and 310mV respectively when the current density is 10mA/cm ^-2 ).

Based on this, the present invention proposes a hollow nanomaterial composited with a hollow metal phosphide and carbon as an electrode material for hydrogen production by catalytic electrolysis of water. Cobalt-loaded polymer hollow nanomaterials were prepared by coordination competition-induced polymerization, followed by carbonization and phosphating to obtain hollow carbon materials containing hollow cobalt phosphide particles, realizing the combination of the two, showing high catalytic activity and stability.

Contents of the invention

The object of the present invention is to provide a dodecahedral hollow cobalt phosphide/carbon composite hollow carbon material doped with hollow cobalt phosphide nanoparticles in situ, a preparation method and its application in catalytic electrolysis of water for hydrogen production. By loading hollow metal phosphides in hollow carbon nanoparticles with dodecahedral morphology, the catalytic activity of the material can be effectively improved. At the same time, the hollow material can provide more active sites, improve the overall stability of the material, make the material have a longer service life, and be more suitable for actual production.

In the present invention, the metal organic framework material ZIF-67 containing cobalt ions is firstly used as a template, and the cobalt ion-doped hollow polymer nanomaterial is prepared by a coordination competition-induced polymerization method. Afterwards, high-temperature carbonization is carried out under the protection of an inert gas atmosphere to obtain cobalt oxide/carbon composite hollow nanomaterials. Finally, the material is phosphated to convert the cobalt oxide into hollow cobalt phosphide nanoparticles, and a hollow cobalt phosphide/carbon composite hollow nanometer material is obtained. The material exhibits excellent performance and excellent stability in catalytic electrolysis of water for hydrogen production.

The raw materials used in the present invention are all commercially available substances, the reaction process is simple, the experimental operation is simple, the conditions are mild, the risk is small, and it has very good repeatability and can be mass-produced.

The hollow cobalt phosphide/carbon composite hollow carbon material with dodecahedral morphology doped in situ with hollow cobalt phosphide nanoparticles according to the present invention can be prepared by the following steps: (1) containing cobalt ions with Preparation of metal-organic framework material ZIF-67 with dodecahedral morphology; (2) Cobalt-containing metal-organic framework material ZIF-67 reacted with dopamine monomer to form hollow polymer nanomaterials containing cobalt coordination doping; (3 ) preparation of cobalt oxide/carbon composite hollow nanomaterial; (4) preparation of hollow cobalt phosphide/carbon composite hollow nanomaterial. specifically,

(1) Preparation of metal-organic framework material ZIF-67 with dodecahedral morphology containing cobalt ions: 200-1000 mg of Co(NO ₃ ) ₂ ·6H ₂ O and 500-3000 mg of 2-methylimidazole were respectively Dissolve in 25-100mL methanol to obtain a clear solution, then mix the two solutions evenly to obtain a purple solution and let it stand at room temperature for 6-24h; then the above-mentioned reaction product is treated by centrifugation (3000-5000rpm, 10-15min), and washed with Washing with methanol for 3 to 5 times, and drying at 40 to 60°C for 10 to 15 hours to obtain a metal organic framework material ZIF-67 with a dodecahedral morphology containing cobalt ions;

(2) Preparation of hollow polymer nanomaterials containing cobalt coordination doping: Weigh 40-60 mg of ZIF-67 prepared in step (1), and disperse it in 50-75 mL of methanol to obtain a ZIF-67 dispersion; Then take 10-15mL, 20mM methanol solution of dopamine hydrochloride, mix the previously obtained ZIF-67 dispersion with the methanol solution of dopamine hydrochloride, and place the reaction system at 40-60°C under reflux and stir for 6-12 hours, the obtained The product was centrifuged (3000-5000rpm, 8-15min) and washed with methanol for 3-5 times until the supernatant was colorless and clear; the supernatant was removed and the solid product was retained to obtain a hollow polymer containing cobalt coordination doping nanomaterials;

(3) Preparation of cobalt oxide/carbon composite hollow nanomaterials: the hollow polymer nanomaterials containing cobalt coordination doping prepared in step (2) were carbonized at 700-800°C for 2 ~4h (heating rate is 3~5°C/min), after cooling to room temperature, cobalt oxide/carbon composite hollow nanomaterials are obtained;

(4) Preparation of hollow cobalt phosphide/carbon composite hollow nanomaterials: Phosphate the cobalt oxide/carbon composite hollow nanomaterials obtained in step (3) under the protection of argon, and the phosphorus source is NaH ₂ PO ₂ ·H ₂ O, the phosphating temperature is 300-400°C, the phosphating time is 1-3h (heating rate 2-5°C/min), and the in-situ doped hollow phosphating described in the present invention is obtained after cooling to room temperature Cobalt nanoparticle hollow cobalt phosphide/carbon composite hollow carbon material with dodecahedral morphology.

Description of drawings

Fig. 1: the transmission electron microscope and the scanning electron microscope photo of the hollow cobalt phosphide/carbon composite hollow nanomaterial prepared in Example 1; (A) is a photo of a transmission electron microscope, and (B) is a photo of a scanning electron microscope;

Figure 2: Transmission electron microscope and scanning electron microscope photographs of the hollow cobalt phosphide/carbon composite hollow nanomaterial prepared in Example 2. (A) is a photo of transmission electron microscope, (B) is a photo of scanning electron microscope;

Fig. 3: the X-ray diffraction spectrum of the hollow cobalt phosphide/carbon composite hollow nanomaterial prepared in Example 1;

Figure 4: The catalytic electrolysis water hydrogen production performance curve of the hollow cobalt phosphide/carbon composite hollow nanomaterial prepared in Example 1; (A) is the linear voltammetry scanning curve, (B) is the Tafel slope curve, (C) is Hydrogen production stability test curve, (D) is the AC impedance spectrum curve.

Detailed ways

The present invention will be further described below in conjunction with examples, but not intended to limit the present invention.

Example 1

(1) Preparation of metal organic framework material ZIF-67 with dodecahedral morphology containing cobalt ions: 498 mg of Co(NO ₃ ) ₂ ·6H ₂ O and 1400 mg of 2-methylimidazole were dissolved in 50 mL of methanol , and then the two solutions were mixed uniformly to obtain a purple solution and stood at room temperature for 6h. The product was purified by centrifugation (5000rpm, 10min), washed three times with methanol, and dried at 60°C for 12h. Finally, a metal-organic framework material ZIF-67 with a dodecahedral morphology was obtained, with a product quality of 400mg.

(2) Preparation of hollow polymer nanomaterials containing cobalt coordination doping: Weigh 760 mg of ZIF-6 prepared in step (1), and disperse it in 75 mL of methanol. After that, 56.9 mg of dopamine hydrochloride was weighed and dissolved in 15 mL of methanol to form a dopamine solution. The ZIF-67 dispersion was mixed with the dopamine solution, and the reaction system was stirred at 60° C. under reflux for 6 h. The obtained product was processed by centrifugation (5000 rpm, 10 min) and washed three times with methanol until the supernatant was colorless and clear, and a cobalt-containing polymer hollow nanomaterial was obtained with a product quality of 25 mg.

(3) Preparation of cobalt oxide/carbon composite hollow nanomaterials: carbonize the prepared hollow polymer nanomaterials at 700°C for 2h under the protection of argon (heating rate is 5°C/min), and cool to room temperature , the cobalt oxide/carbon composite hollow nanomaterial was obtained, and the product quality was 20 mg.

(4) Preparation of hollow cobalt phosphide/carbon composite hollow nanomaterials: under the condition of argon protection, put 20 mg of the hollow material obtained in step (3) on one end of the porcelain boat, and put 500 mg NaH into the other end ₂ Phosphating with PO ₂ ·H ₂ O, the temperature is 300°C, the phosphating time is 2h (heating rate 3°C/min), after cooling to room temperature, the in-situ doped hollow phosphating is obtained Cobalt nanoparticle hollow carbon material with dodecahedral morphology, the product mass is 22 mg.

The size of the prepared hollow cobalt phosphide/carbon composite hollow nanomaterial is about 200-260nm, and its morphology maintains the dodecahedral shape of the template material ZIF-67, and has a hollow structure, and the hollow cobalt phosphide particles are distributed in the hollow space. cavity, as shown in Figure 1. It can be seen from the XRD characterization in Figure 3 that the cobalt in the material exists in the form of cobalt phosphide.

Example 2

(1) Preparation of metal-organic framework material ZIF-67 with dodecahedral morphology containing cobalt ions: 498mg Co(NO ₃ ) ₂ ·6H ₂ O and 700mg 2-methylimidazole were dissolved in 50mL methanol respectively to obtain a purple clear solution, and then the solution was mixed uniformly and allowed to stand at room temperature for 24 h. The product was purified by centrifugation (5000rpm, 10min), washed three times with methanol, and dried at 60°C for 12h. Finally, a metal-organic framework material ZIF-67 with a dodecahedral morphology was obtained, with a product quality of 100mg.

(2) Preparation of hollow polymer nanomaterials containing cobalt coordination doping: Weigh 760 mg of ZIF-6 prepared in step (1), and disperse it in 75 mL of methanol. After that, 56.9 mg of dopamine hydrochloride was weighed and dissolved in 15 mL of methanol to form a dopamine solution. The ZIF-67 dispersion was mixed with the dopamine solution, and the reaction system was placed under reflux at 60° C. and stirred for 12 hours. The obtained product was processed by centrifugation (5000 rpm, 10 min) and washed three times with methanol until the supernatant was colorless and clear, and a cobalt-containing polymer hollow nanomaterial was obtained with a product quality of 25 mg.

(3) Preparation of cobalt oxide/carbon composite hollow nanomaterials: carbonize the prepared hollow polymer nanomaterials at 700°C for 2h under the protection of argon (heating rate is 5°C/min), and cool to room temperature , the cobalt oxide/carbon composite hollow nanomaterial was obtained, and the product quality was 20 mg.

(4) Preparation of hollow cobalt phosphide/carbon composite hollow nanomaterials: under the condition of argon protection, put 20 mg of the hollow material obtained in step (3) on one end of the porcelain boat, and put 500 mg NaH ₂ PO into the other end _2. Phosphating with H ₂ O, the temperature is 300°C, the phosphating time is 2h (heating rate 3°C/min), after cooling to room temperature, the in-situ doped hollow cobalt phosphide described in the present invention is obtained A nanoparticle hollow carbon material with a dodecahedral morphology, the product mass is 22 mg.

The prepared hollow cobalt phosphide/carbon composite hollow nanomaterials have a size of about 450-500nm. cavity, as shown in Figure 2.

Example 3

(1) Preparation of electrocatalytic working electrode: Dissolve 10 mg of the hollow cobalt phosphide/carbon composite hollow nanomaterial prepared in Example 1 in a mixed solvent of 900 μL methanol and 100 μL, 2 wt % perfluorosulfonic acid resin, and ultrasonically Treat for 30 minutes to make it a uniform dispersion. Afterwards, 10 μL of the dispersed liquid was dropped on the glassy carbon electrode and dried at room temperature.

(2) Linear voltammetry test: the voltage range of the linear voltammetry test is 0-0.6V, the scanning speed is 10mV per second, and the electrolyte used is 0.5M sulfuric acid solution.

(3) Catalytic stability test: First, through cyclic voltammetry scanning, the test voltage range is 0-0.6V, the scanning speed is 100mV per second, and the number of scanning cycles is 1000. Then carry out the linear voltammetry sweep test in step (2), and compare the result with the result in step (2).

(4) Electrochemical AC impedance test: In the results obtained by the linear voltammetry test, the corresponding voltage when the current density is 10mA/cm ^-2 is the initial voltage, the high frequency is 10 ⁵ Hz, and the low frequency is 0.1 Hz.

The performance results of catalytic electrolysis of water for hydrogen production are shown in Figure 4. The overpotential of the hollow cobalt phosphide/carbon composite hollow material is only 119mV when the current density is 10mA/cm ^-2 , and it can still maintain good catalytic performance after 1000 cycles. active. The current density only decayed to 90% of the original value after the voltage was continuously applied for 12h. The above results indicate that the material has excellent catalytic activity, high stability and long cycle life.

references

[1] Pan, Y.; Sun, K.; Liu, S.; Cao, X.; Wu, K.; Cheong, W-C.; Chen, Z.; Wang, Y.; Li, Y.; Liu, Y.; Wang, D.; Peng, Q.; Chen, C.; Li, Y.J.Am.Chem.Soc.2018,140,2610-2618.

Claims (3)

1. a kind of preparation method of the hollow carbon material with dodecahedron pattern in situ for adulterating hollow phosphatization cobalt nanoparticle, Its step are as follows：

(1) preparation of the metal-organic framework material ZIF-67 with dodecahedron pattern containing cobalt ions：By 200~ Co (the NO of 1000mg₃)₂·6H₂The 2-methylimidazole of O and 500~3000mg be dissolved separately in 25~100mL methanol obtain it is clear Clear solution, later by two kinds of solution be uniformly mixed obtain purple solution and at room temperature standing 6~for 24 hours；Then by above-mentioned reaction Product wash 3~5 times with methanol by centrifugal treating, 10~15h of drying under the conditions of 40~60 DEG C, obtain containing cobalt from The metal-organic framework material ZIF-67 with dodecahedron pattern of son；

(2) preparation of the hollow polymer nano material containing cobalt coordination doping：Weigh the ZIF- of 40~60mg step (1) preparation 67, it is dispersed in 50~75mL methanol, obtains ZIF-67 dispersion liquid；10~15mL, 20mM Dopamine hydrochloride are taken later The ZIF-67 dispersion liquid being previously obtained is mixed with the methanol solution of Dopamine hydrochloride, and reaction system is placed in by methanol solution It is refluxed 6~12h under the conditions of 40~60 DEG C, the product centrifugal treating that will be obtained, and 3~5 times are washed until supernatant with methanol Liquid achromaticity and clarification；Supernatant is removed, solid product is retained, to obtain the hollow polymer nanometer material for being coordinated doping containing cobalt Material；

(3) cobalt oxide/carbon composite hollow nano material preparation：Step (2) preparation is contained into the hollow poly- of cobalt coordination doping Object nano material is closed under conditions of logical argon gas is protected, be carbonized 2~4h at 700~800 DEG C, is aoxidized after being cooled to room temperature Cobalt/carbon composite hollow nano material；

(4) hollow phosphatization cobalt/carbon composite hollow nano material preparation：Under conditions of the protection of logical argon gas, step (3) is obtained Cobalt oxide/carbon composite hollow nano material carry out phosphatization, phosphorus source NaH₂PO₂·H₂O, phosphatization temperature are 300~400 DEG C, phosphorus The change time is 1~3h, obtained after being cooled to room temperature it is in situ adulterate hollow phosphatization cobalt nanoparticle with dodecahedron pattern Hollow phosphatization cobalt/carbon composite hollow carbon material.

2. a kind of hollow carbon material with dodecahedron pattern in situ for adulterating hollow phosphatization cobalt nanoparticle, feature exist In：It is to be prepared by claim 1 the method.

3. a kind of hollow carbon with dodecahedron pattern in situ for adulterating hollow phosphatization cobalt nanoparticle as claimed in claim 2 Application of the material in catalytic electrolysis aquatic products hydrogen.